Ornamental aquarium is quite fashionable these days. Many people like to cultivate aquatic animals or plants in a fish bowl in homes or offices for pleasure, improving feng shui or as a hobby. In order to constantly maintain the cultivation environment of the fish bowl in a clean condition most breeders try to replenish the water in the fish bowl regularly. To meet this purpose many types of facilities have been developed. For instance, Taiwan patent No. 256996 discloses an excreta collection apparatus located at the bottom of an aquarium. It includes an excreta collection box, a suction tube and a water pump. The excreta collection box is located at the bottom of the aquarium and includes two slant surfaces tilted toward the center. The suction tube is located in the center of the two slant surfaces and connected to the water pump. During collection of excreta filths in the aquarium slide through the two slant surfaces around the suction tube because of the suction force generated by the water pump to the suction tube. Moreover, a liquid supply device also is provided to inject water continuously into the aquarium. The water pump also is set to draw intermittently the water contained the filths around the suction tube. Hence water level in the aquarium changes within a definite range through collaborating of the liquid supply device and the water pump, thereby the filths at the bottom of the aquarium can be removed through suction of the water pump.
In the technique disclosed in the aforesaid patent No. 256996 setting water pump operation conditions requires constant attention of water level dropping range of the aquarium. The relationship between the water level dropping range and operation time and frequency of the water pump can only be accurately determined after a number of trials in setting and adjustment.
Taiwan patent No. M475813 also discloses an automatic cleaning fish breeding apparatus which includes a body, a slant panel and a water directing tube. The slant panel is located at the bottom of the body. The water directing tube is vertically located at a lower position of the slant panel, and includes a top run through one side of the body and bent downward outside the body to form a water outlet. When in use water can be continuously injected into the body through a liquid supply device. When water level has reached the top of water directing tube a siphon phenomenon takes place, namely the water directing tube continuously discharges the water from the body, and excreta of aquatic animals or external filths deposited at the bottom of the body can be discharged with water through the water directing tube until the water level has reached below the water outlet. Then the water level of the body rises again through continuous water injection of the liquid supply device until reaching the top of the water directing tube, and the siphon phenomenon of the water directing tube takes place again. As a result, the water level of the body can be adjusted between the top of the water directing tube and the water outlet, and the filths in the water can be discharged through the water directing tube.
However, the water directing tube disclosed in the aforesaid M475813 merely is an element formed in a single specification, and the elevation of the water outlet cannot be adjusted to change the lowering range of the water level in the body according to the height of different fish bowls or user's requirements, and the siphon phenomenon also cannot be suspended as desired that could cause excessive drop of the water level and affect living environment of the creatures in the fish bowl.